Cold weather storage and Lithium

[Mike & Rebecca]

After experiencing the first winter with an SOK lithium battery, and the trailer in storage, I wish I had purchased the model with a built-in heater. I have realized that with 3-4 months of sub-30-degree nighttime temps, and many days not reaching 30 degrees, there is probably a good portion of the time that the SOK's BMS shut down the ability to receive a charge. Not a big deal when sitting in storage, but it makes it tough if I want to take the trailer out during a break in the weather - I'd have to find some way to "thaw" out the battery first so it could take a charge. But warming the battery is not the question for today.

I've read here and in the Victron MPPT controller manual that you are supposed to disconnect the solar panel from the MPPT before removing the controller to battery connection. I had switches installed on both sides of the MPPT, so I am able to accomplish that.

But what happens when the BMS shuts down charging due to sub-30-degree temperature? Isn't that the same effect as disconnecting the battery from the MPPT controller without disconnecting the solar panel from the MPPT controller first? If I leave the solar running to charge the battery while the trailer is in storage, is the BMS cutoff going to potentially damage the MPPT? Theoretically this same condition will exist if I'm using the trailer in cold temperatures, as the battery is in the unheated front compartment of the 5th wheel.

Do I need to just need to disconnect the solar panel from the MPPT if there's sub-zero temperatures expected?

Thanks!

[Country Campers]

When in storage I would disconnect the solar from the MPPT with your switch. I would also disconnect the battery from the RV, isolate the battery so there is no draw. Another thing you can do is bring the battery into your house or garage, warm storage, then if the weather breaks and you want to use the RV reinstall the battery. I realize the front storage is not heated but I think there is enough residual heat that gets there to keep the battery above the freezing point. I think most if not all of the LIthium batteries have the temp sensor somewhere inside the battery where it will take a while for it to reach the 32 degree mark. There is a duct that runs overhead in the pass thru that has an outlet for heating that area, I thought about plugging into that duct to provide some heat for the front storage.

Brian

[Mike & Rebecca]

Thanks Country Campers! I think you have a similar set up and I followed some of your installation instructions. Yes, I think next year I will pull the battery out November'ish and then keep it at home. I also just purchased the Victron temperature monitor for the BMV 712, and I'm hoping that gives me some accurate info on what's really happening while using the trailer in cold temps. I think I'll also stick my refrigerator temp monitor in the front compartment to get an idea of what the ambient temperature is relative to outside. We're headed out next Friday and it snowed today - so I'm reasonably certain that the nighttime temps during our trip will be in the low 20's. It should be a good test. We'll only be 25 minutes from home.

I"m sure I'll gain confidence the more I use the trailer in cold temps. I just want it to be simple, and I never gave it a second thought with the lead acid batteries. I'm very happy with the SOK lithium, I just need some more experience, so it becomes easier.